U.S. patent application number 10/840106 was filed with the patent office on 2004-12-16 for image data compensation device and method and display system employing the same.
Invention is credited to Cheon, Man-Bok, Cho, Hyun-Sang.
Application Number | 20040252111 10/840106 |
Document ID | / |
Family ID | 33302339 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040252111 |
Kind Code |
A1 |
Cheon, Man-Bok ; et
al. |
December 16, 2004 |
Image data compensation device and method and display system
employing the same
Abstract
An image display device includes an image signal source unit to
provide primary image data and selected compensation data to
compensate the primary image data, and a display unit to display
images using compensated image data obtained by compensating the
primary image data with the selected compensation data. The
selected compensation data is selected from a set of compensation
data in response to variation of ambient temperature of the display
device. The image display device also includes a temperature sensor
to detect the variation of the ambient temperature of the display
device and provide temperature data corresponding to the variation
of the ambient temperature. The image display device also includes
a frequency sensor to detect frequency variation in a vertical
synchronizing signal of the display unit, wherein the selected
compensation data is selected from a set of compensation data in
response to the variation of the ambient temperature and the
frequency variation.
Inventors: |
Cheon, Man-Bok; (Yongin-si,
KR) ; Cho, Hyun-Sang; (Suwon-si, KR) |
Correspondence
Address: |
CANTOR COLBURN LLP
55 Griffin Road South
Bloomfield
CT
06002
US
|
Family ID: |
33302339 |
Appl. No.: |
10/840106 |
Filed: |
May 6, 2004 |
Current U.S.
Class: |
345/204 |
Current CPC
Class: |
G09G 2320/0252 20130101;
G09G 2340/16 20130101; G09G 3/3611 20130101; G09G 3/3648 20130101;
G09G 3/2011 20130101; G09G 2320/0261 20130101; G09G 2310/08
20130101; G09G 2370/045 20130101; G09G 3/2096 20130101; G09G
2320/08 20130101; G09G 2320/041 20130101; G09G 3/20 20130101; G09G
2360/18 20130101 |
Class at
Publication: |
345/204 |
International
Class: |
G09G 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2003 |
KR |
2003-37232 |
Oct 13, 2003 |
KR |
2003-71030 |
Claims
What is claimed is:
1. A display device for displaying images, comprising: an image
signal source unit to provide primary image data and selected
compensation data to compensate the primary image data; and a
display unit to display images using compensated image data
obtained by compensating the primary image data with the selected
compensation data, wherein the selected compensation data is
selected from a set of compensation data in response to variation
of ambient temperature of the display device.
2. The display device of claim 1, further including a temperature
sensor to detect the variation of the ambient temperature of the
display device and provide temperature data corresponding to the
variation of the ambient temperature.
3. The display device of claim 2, wherein the image signal source
unit includes: a data processing part to provide the primary image
data to the display unit; a first memory to store the set of
compensation data, each compensation data being associated with
corresponding one of different temperature ranges; and a first
controller to read the selected compensation data from the first
memory in response to the temperature data from the temperature
sensor and provide the selected compensation data to the display
unit.
4. The display device of claim 3, wherein the set of compensation
data is a plurality of look-up tables of compensation data each of
which is associated with corresponding one of the temperature
ranges.
5. The display device of claim 3, wherein the display unit
includes: a second controller to receive the primary image data
from the data processing part and the selected compensation data
from the first controller and generate the compensated image data;
a data driver to receive the compensated image data and generate
compensated driving voltage signals; and a display panel to receive
the compensated driving voltage signals to display the images.
6. The display device of claim 5, further including a second memory
to store the selected compensation data, the second controller
reading the selected compensation data from the second memory to
compensate the primary image data.
7. The display device of claim 6, wherein the second memory stores
the selected compensation data such that a plurality of look-up
tables of compensation data are each stored at corresponding
address in the second memory and checksum data is assigned to each
of the look-up tables.
8. The display device of claim 5, wherein the second controller
includes: a serial-parallel converting part to convert the selected
compensation data into parallel compensation data; a third memory
to store compensation data associated with characteristics of the
display unit; a first switching part to transfer one of the
parallel compensation data from the serial-parallel converting part
and the compensation data from the third memory in response to a
first clock signal; and a fourth memory to store output of the
first switching part in response to a second clock signal.
9. The display device of claim 8, wherein the first clock signal is
a clock for transferring the selected compensation data from the
second memory to the serial-parallel converting part.
10. The display device of claim 9, wherein the second controller
further includes; a second switching part to transfer one a serial
clock signal and a dot clock signal in response to the first clock
signal; and a third switching part to transfer one of output of the
second switching part and the dot clock signal in response to a
clock signal associated with completion of transfer of the selected
compensation data to the serial-parallel converting part, wherein
an output of the third switching part is provided to the fourth
memory as the second clock signal.
11. The display device of claim 5, wherein the second controller
includes: a serial-parallel converting part to convert the selected
compensation data into parallel compensation data; a buffer to
store the parallel compensation data and generate the parallel
compensation data in response to a buffer control clock; a third
memory to store compensation data associated with characteristics
of the display unit; a first switching part to transfer one of the
parallel compensation data from the buffer and the compensation
data from the third memory in response to a first clock signal; and
a fourth memory to store output of the first switching part in
response to a dot clock signal.
12. The display device of claim 11, wherein the first clock signal
is a clock for transferring the selected compensation data from the
second memory to the serial-parallel converting part.
13. The display device of claim 12, wherein the second controller
further includes; a logic gate to perform logic AND operation with
respect to a vertical synchronizing signal of the display unit and
a clock signal associated with completion of transfer of the
selected compensation data to the serial-parallel converting part;
a second switching part to transfer one a serial clock signal and
the dot clock signal in response to the first clock signal; and a
third switching part to transfer one of output of the second
switching part and the dot clock signal in response to an output of
the logic gate, wherein an output of the third switching part is
provided to the buffer as the buffer control signal.
14. A method of compensating primary image data to increase a
response speed of a display system, comprising: storing a plurality
of look-up tables of compensation data in a memory, each of the
look-up tables being associated with corresponding one of different
temperature ranges; detecting variation of ambient temperature of
the display system; selecting a look-up table of compensation data
in response to the detected variation of the ambient temperature;
and compensating the primary image data using the selected look-up
table of compensation data.
15. The method of claim 14, further including: storing the selected
look-up table of compensation data in a buffer at a current frame;
and compensating the primary image data using the selected look-up
table of compensation data at a next frame, the selected look-up
table of compensation data being transferred from the buffer to a
memory to be accessed during the compensation.
16. The method of claim 15, wherein the transfer of the selected
look-up table of compensation data is performed at a blanking
period between the current and next frames.
17. The method of claim 16, further including: storing the
plurality of look-up tables of compensation data in the memory,
each of the look-up tables being associated with corresponding one
of the different temperature ranges and corresponding one of
different frequency ranges; detecting frequency variation in a
vertical synchronizing signal of the display system; and selecting
a look-up table of compensation data in response to the detected
variation of the ambient temperature and the detected frequency
variation of the vertical synchronizing signal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to image display devices and
method, and more particularly, to a display device and method to
optimize a response time of the display device by compensating
image data using look-up tables of compensation data in association
with temperature variation and frequency variation of the display
device.
[0003] 2. Description of the Related Art
[0004] Liquid crystal display (LCD) devices generally have merits
such as high and uniform luminance, high efficiency, long lifetime,
thin thickness, light weight, low cost and so on. The LCD devices
with such merits have widely used for various types of electronic
goods such as desk-top computers, notebook computers, automotive
navigation systems, television sets, etc.
[0005] In particular, when an LCD device is employed in a
television set, a response time of the LCD device is an important
factor in displaying, especially, moving images. In other words,
compared to other electronic goods, such as computers, mostly
displaying standing images, televisions usually display more moving
images. Since the display quality of moving images is affected by
the response time of an LCD device employed in a television set,
there have been developments to improve the response time of LCD
devices.
[0006] The response time of conventional LCD devices for changing a
gray to another gray is in the range from about 10 ms to about 16
ms. Since the vertical frequency of a television receiver set
according to national television system committee (NTSC) is 60 Hz,
a time period of one (1) frame is about 16.7 ms. Thus, it has been
desired to improve the response time of LCD devices to meet such a
standard.
[0007] The response time of an LCD device is dependent on ambient
temperature of the LCD device. A dielectric constant of liquid
crystal in an LCD device varies depending on the ambient
temperature of the LCD device. A dielectric constant of liquid
crystal aligned parallel with a substrate and a dielectric constant
of liquid crystal aligned perpendicular to the substrate vary in
accordance with variation of the ambient temperature. The
difference between the dielectric constant of the liquid crystal
aligned parallel with the substrate and that of the liquid crystal
aligned perpendicular to the substrate also varies in accordance
with variation of the ambient temperature. This is because the
order parameter of the liquid crystal varies in accordance with
variation of the ambient temperature.
[0008] In addition to the ambient temperature, the response time of
an LCD device also varies in association with a vertical
synchronizing signal of the LCD device. In case that the frequency
of a vertical synchronizing signal of an LCD device is changed, the
response time of the LCD device is also affected by the variation
of the frequency of the vertical synchronizing signal.
[0009] Therefore, a need exists for a display system which provides
quality images by improving the response time of a display device.
Further, it will be advantageous to provide a method of improving
the response time of a display device in association with an
ambient temperature of the display device and a frequency of a
vertical synchronizing signal of the display device.
BRIEF SUMMARY OF THE INVENTION
[0010] The above mentioned and other drawbacks and deficiencies of
the prior art are overcome or alleviated by the enhanced
performance telecommunications connector of the present invention.
In one embodiment, an image display device includes an image signal
source unit to provide primary image data and selected compensation
data to compensate the primary image data, and a display unit to
display images using compensated image data obtained by
compensating the primary image data with the selected compensation
data, in which the selected compensation data is selected from a
set of compensation data in response to variation of ambient
temperature of the display device. The image display device may
also include a temperature sensor to detect the variation of the
ambient temperature of the display device and provide temperature
data corresponding to the variation of the ambient temperature.
[0011] The image signal source unit includes, for example, a data
processing part to provide the primary image data to the display
unit, a first memory to store the set of compensation data in which
each compensation data is associated with corresponding one of
different temperature ranges, and a first controller to read the
selected compensation data from the first memory in response to the
temperature data from the temperature sensor and provide the
selected compensation data to the display unit. The set of
compensation data is look-up tables of compensation data each of
which is associated with corresponding one of the temperature
ranges. The display unit includes, for example, a second controller
to receive the primary image data from the data processing part and
the selected compensation data from the first controller and
generate the compensated image data, a data driver to receive the
compensated image data and generate compensated driving voltage
signals, and a display panel to receive the compensated driving
voltage signals to display the images. The image display device may
also include a second memory to store the selected compensation
data so that the second controller reads the selected compensation
data from the second memory to compensate the primary image data.
The second memory may store the selected compensation data such
that the look-up tables of compensation data are each stored at
corresponding address in the second memory and checksum data is
assigned to each of the look-up tables.
[0012] The second controller includes, for example, a
serial-parallel converting part to convert the selected
compensation data into parallel compensation data, a third memory
to store compensation data associated with characteristics of the
display unit, a first switching part to transfer one of the
parallel compensation data from the serial-parallel converting part
and the compensation data from the third memory in response to a
first clock signal which is a clock for transferring the selected
compensation data from the second memory to the serial-parallel
converting part, and a fourth memory to store output of the first
switching part in response to a second clock signal. The second
controller may also include a second switching part to transfer one
a serial clock signal and a dot clock signal in response to the
first clock signal, and a third switching part to transfer one of
output of the second switching part and the dot clock signal in
response to a clock signal associated with completion of transfer
of the selected compensation data to the serial-parallel converting
part, in which an output of the third switching part is provided to
the fourth memory as the second clock signal.
[0013] In another embodiment, the second controller includes a
serial-parallel converting part to convert the selected
compensation data into parallel compensation data, a buffer to
store the parallel compensation data and generate the parallel
compensation data in response to a buffer control clock, a third
memory to store compensation data associated with characteristics
of the display unit, a first switching part to transfer one of the
parallel compensation data from the buffer and the compensation
data from the third memory in response to a first clock signal
which is a clock for transferring the selected compensation data
from the second memory to the serial-parallel converting part, and
a fourth memory to store output of the first switching part in
response to a dot clock signal. The second controller may also
include a logic gate to perform logic AND operation with respect to
a vertical synchronizing signal of the display unit and a clock
signal associated with completion of transfer of the selected
compensation data to the serial-parallel converting part, a second
switching part to transfer one a serial clock signal and the dot
clock signal in response to the first clock signal, and a third
switching part to transfer one of output of the second switching
part and the dot clock signal in response to an output of the logic
gate, in which an output of the third switching part is provided to
the buffer as the buffer control signal.
[0014] In another embodiment, the image display device includes a
frequency sensor to detect frequency variation in a vertical
synchronizing signal of the display unit. The selected compensation
data is selected from a set of compensation data in response to the
variation of the ambient temperature and the frequency
variation.
[0015] In another embodiment, a method of compensating primary
image data to increase a response speed of a display system,
includes storing a plurality of look-up tables of compensation data
in a memory in which each of the look-up tables is associated with
corresponding one of different temperature ranges, detecting
variation of ambient temperature of the display system, selecting a
look-up table of compensation data in response to the detected
variation of the ambient temperature, and compensating the primary
image data using the selected look-up table of compensation data.
The method may also include storing the selected look-up table of
compensation data in a buffer at a current frame, and compensating
the primary image data using the selected look-up table of
compensation data at a next frame, in which the selected look-up
table of compensation data is transferred from the buffer to a
memory to be accessed during the compensation.
[0016] In another embodiment, the method further includes storing
the plurality of look-up tables of compensation data in the memory
in which each of the look-up tables is associated with
corresponding one of the different temperature ranges and
corresponding one of different frequency ranges, detecting
frequency variation in a vertical synchronizing signal of the
display system, and selecting a look-up table of compensation data
in response to the detected variation of the ambient temperature
and the detected frequency variation of the vertical synchronizing
signal.
[0017] These and other objects, features and advantages of the
present invention will become apparent from the following detailed
description of illustrative embodiments thereof, which is to be
read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other advantages of the present invention will
become more apparent by describing in detail exemplary embodiments
thereof with reference to the accompanying drawings, in which:
[0019] FIG. 1 is a graph comparing a response time of liquid
crystal in association with various ambient temperatures of a
display device;
[0020] FIG. 2 is a schematic diagram illustrating an equivalent
circuit of a pixel of an LCD device;
[0021] FIG. 3 is a graph illustrating data and pixel voltages in an
LCD device;
[0022] FIG. 4 is a graph illustrating transmittance of an LCD
device;
[0023] FIG. 5 is a block diagram illustrating a display system
according to an exemplary embodiment of the present invention;
[0024] FIG. 6 is a block diagram illustrating the image signal
source in FIG. 5 according to an exemplary embodiment of the
present invention;
[0025] FIG. 7 is a block diagram illustrating the LCD device in
FIG. 5 according to an exemplary embodiment of the present
invention;
[0026] FIG. 8 is a block diagram illustrating the timing control
part in FIGS. 5 and 7 according to an exemplary embodiment of the
present invention;
[0027] FIG. 9 is a block diagram illustrating the timing control
part in FIGS. 5 and 7 according to another exemplary embodiment of
the present invention;
[0028] FIG. 10 is a timing diagram for describing the operation of
the timing control part in FIG. 9; and
[0029] FIG. 11 is a schematic diagram illustrating the LUTs of
compensation data stored in a memory of the LCD device in FIGS. 5
and 7 and checksum data of the LUTs.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Detailed illustrative embodiments of the present invention
are disclosed herein. However, specific structural and functional
details disclosed herein are merely representative for purposes of
describing exemplary embodiments of the present invention.
[0031] FIG. 1 is a graph comparing a response time of liquid
crystal in association with various ambient temperatures of a
display device in middle gray. Referring to FIG. 1, the liquid
crystal is activated in association with the ambient temperature
such that the liquid crystal is more readily activated as the
ambient temperature increases. Thus, the response time of the
liquid crystal increases in proportion to the increase in the
ambient temperature.
[0032] Since display devices, such as LCD devices, displaying
moving images operate in various temperatures (e.g., room
temperature, below-zero temperature, etc.), capability of
maintaining an optimized response time of a display device in the
various temperatures is an important factor for displaying quality
images. In case that a display device is operated in a below-zero
temperature, the response time of the display device decreases so
that the display quality of moving images is deteriorated.
[0033] FIG. 2 is a schematic diagram illustrating an equivalent
circuit of a pixel of an LCD device. An LCD device includes pixels
each of which is defined by corresponding gate and data lines. A
scan signal is provided to the gate lines, and a data signal is
provided to the data lines. Each pixel includes a switching element
electrically connected to the gate and data lines. The pixels are
arranged in a matrix form in the LCD device.
[0034] Referring to FIG. 2, the pixel of an LCD device includes a
thin film transistor (TFT) 10, a liquid crystal capacitor CLC and a
storage capacitor CST. A source electrode of the TFT 10 is
electrically connected to a data line Dp, and a gate electrode of
the TFT 10 is electrically connected to a gate line GQ. The liquid
crystal capacitor CLC has capacitance formed by liquid crystal
disposed at corresponding one of the pixels in the LCD device. In
other words, the liquid crystal capacitor CLC is equivalent to the
liquid crystal disposed between a drain electrode of the TFT 10 and
a common electrode in the LCD device. The storage capacitor CST is
electrically connected to the drain electrode of the TFT 10.
[0035] When a gate-on signal is applied to the gate line GQ and the
TFT 10 is turned-on, a data voltage VD is applied from the data
line Dp to a pixel electrode (not shown) through the TFT 10. An
electric field is formed by a voltage difference between a pixel
voltage Vp applied to the pixel electrode and a common voltage Vcom
to vary light transmittance of the liquid crystal disposed between
the pixel electrode and the common electrode. The storage capacitor
C.sub.ST maintains the voltage difference during a time period of
one frame.
[0036] The liquid crystal is dielectric anisotropic material so
that a dielectric constant of the liquid crystal varies with
respect to a direction of molecules of the liquid crystal.
Therefore, when a voltage is applied between the pixel electrode
and the common electrode, a capacitance of the liquid crystal
capacitor C.sub.LC varies with respect to a variation of the
dielectric constant of the liquid crystal. Charge is applied to the
liquid crystal capacitor C.sub.LC while the TFF 10 is turned on,
and the pixel voltage (Vp) applied to the liquid crystal varies in
accordance to the capacitance of the liquid crystal (C.sub.LC).
Here, the relationship of charge Q, capacitance C, and voltage V is
represented by the following Equation 1.
Q=CV Equation 1
[0037] In twisted nematics (TN) liquid crystal which is normally
white mode, molecules of the liquid crystal are arranged parallel
with a substrate of the LCD device when the pixel voltage is about
0V.
[0038] The capacitance of the liquid crystal C.sub.LC is
represented by Equation 2.
C.sub.LC(0V)=.epsilon..sub..perp.A/d Equation 2
[0039] Here, `.epsilon..sub..perp.` denotes a dielectric constant
of the liquid crystal of which molecules are arranged perpendicular
to a direction of the light that is applied to the liquid crystal,
`A` denotes an areal size of the LCD substrate, and `d` denotes a
distance between substrates of the LCD device.
[0040] When the pixel voltage is about 5V, the liquid crystal
molecules are arranged parallel with the substrate so that the
display mode becomes full-black. In this case, the capacitance of
the liquid crystal C.sub.LC is represented by Equation 3.
C.sub.LC(5V)=.epsilon..sub..parallel.A/d Equation 3
[0041] Here, `.epsilon..sub..parallel.` denotes a dielectric
constant of the liquid crystal of which molecules are arranged
parallel with a direction of the light applied to the liquid
crystal. Since dielectric constant `.epsilon..sub..parallel.` is
larger than dielectric constant `.epsilon..sub..perp.`, the
capacitance of the twisted nematic liquid crystal increases in
proportion to the pixel voltage applied to the liquid crystal.
[0042] A charge of the TFT for displaying full-black in an [n]th
frame needs to be about C.sub.LC(5V).times.5V. Assuming that the
full-white was displayed in the [n-1]th frame, the capacitance of
the liquid crystal is about C.sub.LC(0V) in the [n]th frame because
the liquid crystal molecules do not effectively change the
arrangement while the TFT is turned on. In other words, the voltage
applied to the pixel electrode for displaying the full-white is
about 0V in the [n-1]th frame. Although the data voltage is about
5V in the [n]th frame to display the full-black, the charge of the
pixel electrode is about C.sub.LC(0V).times.5V. Since capacitance
C.sub.LC(0V) is less than capacitance C.sub.LC(5V), the pixel
voltage Vp in the [n]th frame is less than 5V (e.g., about 3.5V).
As a result, the full-black is not effectively displayed.
[0043] Also, when the data voltage VD of about 5V is applied in the
[n+1]th frame to display the full-black, the charge of the liquid
crystal is about C.sub.LC(3.5V).times.5V so that the pixel voltage
Vp is increased. In other words, the pixel voltage Vp becomes in
the range from about 3.5V to about 5V in the [n+1]th frame. In like
manner, the data voltage VD of 5V is applied and the pixel voltage
Vp increases in the subsequent frames until the pixel voltage Vp
becomes or approximates 5V.
[0044] When the gray-scale of a pixel is changed, the gray-scale of
the present frame is dependent on the gray-scale of the previous
frame so that a pixel has a desired gray-scale after several
frames. In like manner, when the transmittance of the liquid
crystal is changed, the transmittance of the present frame is
dependent on the transmittance of the previous frame so that the
liquid crystal has a desired transmittance after several
frames.
[0045] Assuming that the full-black is displayed in the [n-1]th
frame and the pixel voltage Vp of 5V is applied to the pixel in the
[n]th frame, the charge of the pixel is about C.sub.LC(5V).times.5V
so that the pixel voltage Vp of the liquid crystal is about 5V.
Accordingly, the full-black is effectively displayed in the [n]th
frame. Therefore, the pixel voltage Vp of the present frame is
dependent on the pixel voltage Vp of the previous frame as well as
the data voltage of the present frame.
[0046] FIG. 3 is a graph illustrating data and pixel voltages in an
LCD device, and FIG. 4 is a graph illustrating transmittance of an
LCD device. FIGS. 3 and 4 show the results of the experiments in
which the LCD device is operated without consideration of the
effect of previous frames.
[0047] Referring to FIG. 3, a data voltage VD substantially equal
to a desired pixel voltage Vw is applied to the pixel in frames N
to N+3. As shown in FIG. 3, the pixel voltage (Vp) of the liquid
crystal is less than the desired pixel voltage Vw in frames N to
N+2, and it becomes approximate to the desired pixel voltage Vw in
the [N+3]th frame. Referring to FIG. 4, the liquid crystal also has
a desired transmittance after several frames.
[0048] In contrast, in the present invention, a pixel signal (Pn-1)
of the previous frame is compared with a pixel signal (Pn+1) of the
next frame to generate a compensation pixel signal (Pn') for the
present frame. The compensation pixel signal (Pn') is applied to an
pixel electrode of the LCD device in the present frame. In case of
an analog type LCD device, the pixel signal (Pn) is a data voltage.
On the other hand, in case of a digital type LCD device, the pixel
signal (Pn) is gray-scale of binary data to control the data
voltage. In this case, the gray-scale data is compensated so as to
compensate the data voltage applied to each pixel.
[0049] When the pixel signal (i.e., the data voltage or the
gray-scale data) of the present frame is substantially equal to
that of the previous frame, the pixel signal is not compensated.
When the gray-scale data of the present frame is larger than that
of the previous frame, compensated gray-scale data larger than the
gray-scale signal of the present frame is outputted. When the
gray-scale data of the present frame is smaller than that of the
previous frame, the compensated gray-scale data smaller than the
gray-scale data of the present frame is outputted. The amount of
the compensation is in proportion to the difference between the
gray-scale data of the frames.
[0050] FIG. 5 is a block diagram illustrating a display system
according to an exemplary embodiment of the present invention.
Referring to FIG. 5, the display system includes a image signal
source 100 and an LCD device 200. The image signal source 100
outputs primary gray-scale data RGB and compensation data 132, and
the LCD device 200 displays images by using the primary gray-scale
data and the compensation data.
[0051] The image signal source 100 includes a data processing part
110, a synchronous dynamic random access memory (SDRAM) 120, and a
micro controller 130. The image signal source 100 outputs the
primary gray-scale data RGB to the LCD device 200 for displaying
images thereon, and outputs the compensation data 132 in response
to temperature data 52 detected by and provided from a temperature
sensor 50. The image signal source 100 is, for example, a computer,
a signal processing block of a television receiver set, etc,
electrically connected to the LCD device 200.
[0052] The data processing part 110 outputs the primary gray-scale
data provided to the LCD device 200. The primary gray-scale data
includes red (R) primary gray-scale data, green (G) primary
gray-scale data and blue (B) primary gray-scale data.
[0053] The SARM 120 stores look-up tables (LUTs) of compensation
data to optimize the response time of the LCD device 200. The LUTs
are each associated with corresponding one of different temperature
ranges. In other words, each LUT contains compensation data for a
selected temperature range. The micro controller 130 selects an LUT
of compensation data in response to the temperature data 52
provided from the temperature sensor 50 and outputs the selected
LUT of compensation data to the LCD device 200.
[0054] The LCD device 200 includes a timing control part 210, a
first memory 220, a second memory 230, a data driver 240 and an LCD
panel 250. For example, the first memory 220 is implemented with an
electrical erasable programmable read only memory (EEPROM), and the
second memory 230 is implemented with a synchronous dynamic random
access memory (SDRAM). In the LCD device 200, the timing control
part 210 provides compensated gray-scale data R'G'B' to the data
driver for driving the LCD panel 250. The compensated gray-scale
data is obtained from the primary gray-scale data and the
compensation data 132 provided from the image signal source 100 to
improve (i.e., decrease) the response time of the LCD device 200.
The compensated gray-scale data includes red (R') compensated
gray-scale data, green (G') compensated gray-scale data and blue
(B') compensated gray-scale data. The compensated gray-scale data
R'G'B' is associated with the ambient temperature of the display
system and updated in accordance with variation of the ambient
temperature.
[0055] When the primary gray-scale data is provided from the data
processing part 110 to the timing control part 210, the timing
control part 210 processes the primary gray-scale data of the
previous and present frames to generate the compensated gray-scale
data. Thus, the compensation gray-scale data improves the time
response of the LCD device owing to the process of the primary
gray-scale data of the previous and present frames and the
compensation data associated with the different temperature
ranges.
[0056] The compensation data 132 provided from the micro controller
130 is stored in the first memory 220 (e.g., EEPROM). The
compensation data 132 is to compensate the gray-scale data based on
the ambient temperature of the display system and is selected from
the LUTs of compensation data in accordance with the temperature
data 52 generated from the temperature sensor 50. The compensation
data stored in the first memory 220 in an LUT form is read out by
the timing control part 210.
[0057] For example, in case that the primary gray-scale data is
8-bit data, the compensation data may be 8-bit data or 4- or 6-bit
data. If the compensation data is 4- or 6-bit data, the 4- or 6-bit
data of the primary gray-scale data is compensated by the LUT of
compensation data and remaining-bit data is compensated using an
interpolation method so as to decrease the response time.
[0058] The timing control part 210 controls read/write operation of
the primary gray-scale data from/into the second memory 230 (e.g.,
SDRAM). The timing control part 210 supplies the compensated
gray-scale data to the data driver 240, and the data driver 240
transforms the compensated gray-scale data to an analog voltage
signal. Then, the analog voltage signal is provided to the LCD
panel 250 via data lines of the LCD device 200.
[0059] In case that the ambient temperature is below zero in
Celsius, the response time of the liquid crystal is improved (i.e.,
decreased) by compensating the gray-scale data using an LUT of
compensation data appropriate for the below-zero temperature range.
In contrast, when the ambient temperature is increased, the
response time of the liquid crystal is also improved by
compensating the gray-scale data using an LUT of compensation data
appropriate for the increased temperature range.
[0060] The LUT of compensation data stored in the first memory 220
is changed in response to variation of the ambient temperature
which is sensed by the temperature sensor 50. The micro controller
130 reads out an appropriate LUT of compensation data from the
SDRAM 120 in response to the temperature data 52 provided from the
temperature sensor 50, and the appropriate LUT of compensation data
is stored in the firs memory 220. The timing control part 210
compensates the primary gray-scale data using the appropriate LUT
of compensation data to optimize the response time of the display
system at the given ambient temperature. Further, for example,
power of the LCD device 200 is controlled in response to the
variation of the compensation data so as to prevent malfunction of
a lamp of the LCD device. Also, an I.sup.2C bus (not shown)
electrically connecting the micro controller 130 to the first
memory 220 may be controlled to change the LUT of compensation data
in the first memory 220.
[0061] When the LUT of compensation data is stored in the first
memory 220, the micro controller 130 directly controls the timing
control part 210 so that the compensation data is downloaded from
the first memory 220 into a read only memory (ROM) in the timing
control part 210. In case that a time period of changing the LUT of
compensation data is long, a predetermined alarm message stored in
the memory 120 of the image signal source 100 is displayed on the
LCD panel 250.
[0062] FIG. 6 is a block diagram illustrating the image signal
source in FIG. 5 according to an exemplary embodiment of the
present invention. Referring to FIG. 6, the image signal source 100
includes the data processing part 110, a first memory 120, a second
memory 125, the micro controller 130, an analog-digital converter
135, and a voltage generating part 140. The first and second
memories 120 and 125 are, for example, synchronous dynamic random
access memories (SDRAMs).
[0063] The data processing part 110 outputs primary gray-scale data
RGB to display images. The primary gray-scale data includes red
primary gray-scale data R, green primary gray-scale data G, and
blue primary gray-scale data B.
[0064] The compensation data for improving the response time of
liquid crystal is stored in the first memory 120 in the form of
look-up tables. The LUTs of compensation data stored in the first
memory 120 are each associated with corresponding one of different
temperature ranges. For example, the first LUT of compensation data
contains the compensation data for a temperature range from
-10.degree. C. to 0.degree. C., the second LUT of compensation data
contains the compensation data for a temperature range from
0.degree. C. to 10.degree. C., the third LUT of compensation data
contains the compensation data for a temperature range from
10.degree. C. to 20.degree. C., and the fourth LUT of compensation
data contains the compensation data for a temperature range from
20.degree. C. to 30.degree. C.
[0065] The second memory 125 stores on-screen display (OSD) data
for classified characteristic values of the display system. The
classified characteristic values may be changed by a user using
switches on the display system or its remote controller. The image
signal source 100, such as a television receiver set, includes an
OSD unit having the OSD data. The image signal source includes an
OSD unit for controlling the response speed of the liquid crystal
of the LCD device. For example, the OSD unit includes a temperature
response mode and a reference value mode.
[0066] The micro controller 130 provides the compensation data 132,
horizontal and vertical synchronizing signals Hsync and Vsync, a
data enable signal DE, and a main clock MCLK to the LCD device 200
to display the primary gray-scale data outputted from the data
processing part 110. The micro controller 130 supplies the
compensation data 132 in an LUT form corresponding to a selected
temperature range in response to the temperature data provided
through the analog-digital converter 135. The analog-digital
converter 135 converts a analog signal of the temperature data into
digital data.
[0067] When the temperature data is applied to the micro controller
130, the LUT of compensation data corresponding to the temperature
data is selected from the first memory 120 and provided to the LCD
device 200. The LUT of compensation data is transferred, for
example, through an inter-IC (I.sup.2C) bus that is a parallel bus
including two data lines.
[0068] The voltage generating part 140 generates a voltage for the
micro controller 130. For example, the voltage generating part 140
is independent of a power source of the display system so as to
prevent malfunction of the micro controller 130.
[0069] FIG. 7 is a block diagram illustrating the LCD device in
FIG. 5 according to an exemplary embodiment of the present
invention. Referring to FIG. 7, the LCD device includes the timing
control part 210, the first memory 220, the second memory 230, the
data driver 240, the LCD panel 250, a scan driver 260, and a
voltage generating part 270. The first memory 220 is, for example,
an electrical erasable programmable read only memory (EEPROM), and
the second memory 230 is, for example, a synchronous dynamic random
access memory (SDRAM).
[0070] The micro controller 130 of the image signal source 100
provides the primary gray-scale data, the synchronizing signals
(Hsunc, Vsync), the data enable signal (DE) and the main clock
(MCLK) to the timing control part 210. The primary gray-scale data
includes red (R) primary gray-scale data, green (G) primary
gray-scale data and blue (B) primary gray-scale data. The timing
control part 210 provides the compensated gray-scale data and data
driving signals (LOAD, STH) for outputting the compensated
gray-scale data to the data driver 240, and also provides scan
driving signals (GATE CLK and STV) to the scan driver 260. The
compensated gray-scale data includes red (R') compensated
gray-scale data, green (G') compensated gray-scale data and blue
(B') compensated gray-scale data.
[0071] The micro controller 130 provides a selected LUT of
compensation data 132 to the timing control part 210. The selected
LUT of compensation data is stored in the first memory 220 and then
read out by the timing control part 210. In another embodiment, the
LUT of compensation data 132 is directly stored in an internal
memory (not shown) of the timing control part 210.
[0072] The data processing part 110 of the image signal source 100
provides the primary gray-scale data to the timing control part
210. The gray-scale data of the present frame is compared with the
gray-scale data of the previous frame to determine the compensated
gray-scale data of the present frame. The compensated gray-scale
data is provided to the data driver 240 so that the response speed
of liquid crystal is increased.
[0073] The first memory 220 stores the LUTs of compensation data
132. Each of the LUTs of compensation data 132 contains
compensation information (or compensation amount) in a selected
temperature range. When the ambient temperature is changed, the
micro controller 130 selects and supplies an LUT of compensation
data corresponding to the changed ambient temperature to the first
memory 220, and then the selected LUT of compensation data is
provided to the timing control part 210 from the first memory
220.
[0074] The primary gray-scale data is stored in the second memory
230. The second memory 230 includes a first memory bank 232 and a
second memory bank 234. When a half of the primary gray-scale data
of the present frame is written in the first memory bank 232 by the
timing control part 210, the timing control part 210 reads a half
of the primary gray-scale data of the previous frame from the
second memory bank 234. Also, when the timing control part 210
reads the half of the primary gray-scale data of the previous frame
from the second memory bank 234, the half of the primary gray-scale
data of the present frame may be written in the first memory bank
232 by the timing control part 210. With the first and second
memory banks 232 and 234 of the second memory 230, the reading and
writing operations are performed simultaneously and
continuously.
[0075] The data driver 240 receives the compensated gray-scale data
R'G'B' from the timing control part 210 and provides the data
signals D1-D.sub.M to data lines, respectively, of the LCD panel
250. The timing control part 210 supplies the scan driving signals
(GATE CLK, STV) to the scan driver 260 which then provides gate-on
signals S1-S.sub.N for turning on switch elements in the LCD panel
250.
[0076] In the LCD panel 250, the gate lines are scan lines for
transmitting the gate-on signals S1-S.sub.N and the data lines are
source lines for transmitting the data signals D1-D.sub.M. The LCD
panel 250 includes multiple pixels each of which is defined by the
adjacent gate and data lines. Each pixel includes a thin film
transistor (TFT) 110 as the switching element, a liquid crystal
capacitor C.sub.LC and a storage capacitor C.sub.ST. Gate and
source electrodes of the TFT are electrically connected to the gate
and source lines, respectively. The liquid crystal capacitor
C.sub.LC is electrically connected to a drain electrode of the
TFT.
[0077] The second voltage generating part 270 controls electric
power of the LCD device. When the LUT of compensation data is
written in the first memory 220, the second voltage generating part
270 controls the electric power of the LCD device so as to prevent
malfunction.
[0078] In the embodiment of FIGS. 5-7, the display system employs
the digital interface such that the digital gray-scale data is
provided from the image signal source to the LCD device. However,
it would obvious to one skilled in the art that the LCD device
includes an interface unit for processing an analog signal
externally provided to the LCD device to transform it into the
digital data.
[0079] FIG. 8 is a block diagram illustrating the timing control
part in FIGS. 5 and 7 according to an exemplary embodiment of the
present invention. Referring to FIG. 8, the timing control part 210
includes a serial-parallel converting part 2110, a first memory
(e.g., read only memory or ROM) 2120, a first switching part 2130,
a second switching part 2140, a third switching part 2150, and a
second memory (e.g., random access memory or RAM) 2160. The LUTs of
compensation data are stored in memory 220, and an LUT of
compensation data is selected based on LUT select signals
externally provided, for example, from the television receiver set.
The selected LUT of compensation data is stored in memory 2160, and
the timing control part 210 compensates the gray-scale data in
accordance with the selected LUT stored in memory 2160. The first
to third switching parts 2130, 2140 and 2150 are each implemented
with, for example, a multiplexer.
[0080] The LUT of compensation data read from memory 220 is
provided to the serial-parallel converting part 2110 which converts
the serial type compensation data into parallel type compensation
data. Memory 2120 also stores compensation data set by a
manufacturer of the display system. The compensation data in memory
2120 is to optimize the response time of the display system in
consideration of characteristics of the LCD device. Here, for the
purpose of description convenience, the compensation data output
from the serial-parallel converting part 2110 is called "first
compensation data," and the compensation data output from memory
2120 is called "second compensation data."
[0081] The first and second compensation data are provided to the
first switching part 2130, and one of them is selected and output
from the first switching part 2130 in response to a first control
signal which is, for example, a transmission clock I.sup.2C_LI. The
selected compensation data in the first switching part 2130 is
provided to and stored in memory 2160. In this embodiment, the
transmission clock I.sup.2C_LI is a clock for transmitting the
first compensation data output from the serial-parallel converting
part 2110. For example, the first switching part 2130 transfers the
first compensation data from the serial-parallel converting part
2110 to memory 2160 when the transmission clock I.sup.2C_LI is
active (e.g., logic high), and the first switching part 2130
transfers the second compensation data from memory 2120 to memory
2160 when the transmission clock I.sup.2C_LI is inactive (e.g.,
logic low). The transmission clock I.sup.2C_LI is also a clock for
transferring the selected LUT of compensation data to the
serial-parallel converting part 2110.
[0082] The second switching part 2140 receives a serial clock SCL
and a dot clock DCLK and outputs one of them in response to the
transmission clock I.sup.2C_LI. The serial clock SCL is associated
with the transmission clock I.sup.2C_LI, the dot clock is
associated with the primary gray-scale data provided from the image
signal source. The selected one of the serial clock SCL and the dot
clock DCLK is then provided to the third switching part 2150. For
example, the second switching part 2140 transfers the serial clock
SCL to the third switching part 2150 when the transmission clock
I.sup.2C_LI is active (e.g., logic high), and the second switching
part 2140 supplies the dot clock DCLK to the third switching part
2150 when the transmission clock I.sup.2C_LI is inactive (e.g.,
logic low).
[0083] The third switching part 2150 receives the output of the
second switching part 2140 and the dot clock DCLK and outputs one
of the input signals in response to a transmission termination
clock I.sup.2C_DONE, which is a clock associated with completion of
the transfer of the selected compensation data from memory 220 to
the serial-parallel converting part 2110. For example, the third
switching part 2150 transfers the dot clock DCLK when the
transmission termination clock I.sup.2C_DONE is active (e.g., logic
high), and the third switching part 2150 transfers the output of
the second switching part 2140 when the transmission termination
clock I.sup.2C_DONE is inactive (e.g., logic low). The output of
the third switching part 2150 is then provided to memory 2160 as a
third control signal. The third control signal is a clock signal,
either the dot clock signal DCLK or the output clock signal from
the second switching part 2150, to be used in writing operation of
the compensation data output from the first switching part 2130. In
other words, the compensation data output from the first switching
part 2130 is stored in memory 2160 in response to the third control
signal, i.e., a clock signal output from the third switching part
2150.
[0084] As described above, the time response (or response speed) of
the LCD device is affected by variation of ambient temperature.
Thus, the time response is improved by compensating the gray-scale
data using the LUTs of compensation data each associated with
corresponding one of different temperature ranges.
[0085] In addition to the variation of the ambient temperature, the
time response of the LCD device is affected by a frequency of the
vertical synchronizing signal used for the display system. While
the compensation amount becomes smaller in the compensation for the
ambient temperature variation as the ambient temperature becomes
higher, the compensation amount becomes larger in the compensation
for the frequency variation of the vertical synchronizing signal as
the frequency becomes higher. This is because when the frequency of
the vertical synchronizing signal is increased, a time period of a
frame is decreased so that the compensation amount needs to be
increased.
[0086] The first compensation data (i.e., the selected LUT of
compensation data) is stored in memory 2160 in response to the
serial clock SCL that is slower than the dot clock DCLK.
Accordingly, the first compensation data is stored in memory 2160
for a time period of several frames including frame blanking
periods. The electric power is continuously supplied to the LCD
device while the first compensation data is stored in memory 2160.
In this case, when moving images are displayed, malfunction such as
a noise, an LUT having inverted color, deformation of a gray-scale,
etc., may be displayed on the LCD device due to superposed data and
a delay of loading time. For example, real-time inputted gray-scale
data is superposed with overshooted data corresponding to the LUT
to form the superposed data. The display malfunction may occur
because the data corresponding to one frame includes an LUT of
compensation data corresponding to a temperature range before a
temperature variation and an LUT of compensation data corresponding
to a temperature range after the temperature variation.
[0087] FIG. 9 is a block diagram illustrating the timing control
part in FIGS. 5 and 7 according to another exemplary embodiment of
the present invention. Referring to FIG. 9, the timing control part
210 includes a serial-parallel converting part 2210, a first
switching part 2220, an AND gate 2230, a second switching part
2240, a first memory (e.g., ROM) 2250, a buffer 2260, a third
switching part 2270, and a second memory (e.g., RAM) 2280. Multiple
LUTs of compensation data is stored in memory 220 (e.g., EEPROM).
The timing control part 210 determines an LUT in response to a LUT
selection signal provided from a television receiver set, and the
selected LUT is stored in memory 2280 to be used for the
compensation. The first to third switching parts 2220, 2240 and
2270 are each implemented with, for example, a multiplexer.
[0088] The selected LUT of compensated data is read from memory 220
and provided to the serial-parallel converting part 2210 in which
the serial data is converted into the parallel data. Memory 2250
also stores compensation data set by a manufacturer of the display
system. The compensation data in memory 2250 is to optimize the
response time of the display system in consideration of
characteristics of the LCD device. Here, for the purpose of
description convenience, the compensation data output from the
serial-parallel converting part 2110 is called "first compensation
data," and the compensation data output from memory 2250 is called
"second compensation data."
[0089] The first switching part 2220 receives the serial clock SCL
and the dot clock DCLK and outputs one of them in response to the
transmission clock I.sup.2C_LI. For example, the first switching
part 2220 outputs the serial clock SCL to the second switching part
2240 when the transmission clock I.sup.2C_LI is active, and the
first switching part 2220 outputs the dot clock DCLK to the second
switching part 2240 when the transmission clock I.sup.2C_LI is
inactive.
[0090] The AND gate 2230 receives a vertical synchronizing signal
V.sub.SYNC and the transmission termination clock I.sup.2C_DONE and
performs AND operation with respect to the input signals. An output
of the AND gate 2230 is provided to the second switching part
2240.
[0091] The second switching part 2240 receives the clock outputted
from the first switching part 2220 and the dot clock DCLK and
outputs one of them in response to the output signal of the AND
gate 2230. For example, the second switching part 2240 outputs the
clock outputted from the first switching part 2220 when the output
of the AND gate 2230 is active, and the second switching part 2240
outputs the dot clock DCLK when the output of the AND gate 2230 is
inactive. The output of the second switching part 2240 is provided
to the buffer 2260.
[0092] The buffer 2260 stores the first compensation data from the
serial-parallel converting part 2210 and outputs the first
compensation data to the third switching part 2270 in response to
the clock outputted from the second switching part 2240. In this
embodiment, the buffer 2260 outputs the first compensation data to
the third switching part 2270 when the dot clock DCLK is supplied
to the buffer 2260 from the second switching part 2240, and the
first compensation data is not outputted when the serial clock SCL
is applied to the buffer 2260 from the second switching part
2240.
[0093] The third switching part 2270 outputs one of the first
compensation data outputted from the buffer 2260 and the second
compensation data outputted from memory 2250 in response to the
transmission clock I.sup.2C_LI. The output of the third switching
part 2270 is provided to memory 2280. When the transmission clock
I.sup.2C_LI is active, the third switching part 2270 outputs the
first compensation data outputted from the buffer 2260 to memory
2280. When the transmission clock I.sup.2C_LI is inactive, the
third switching part 2270 outputs the compensation data outputted
from memory 2250 to memory 2280. The compensation data output from
the third switching part 2270 is stored in memory 2280 in response
to the dot clock DCLK.
[0094] FIG. 10 is a timing diagram for describing the operation of
the timing control part in FIG. 9, in which the LUT of compensation
data is changed during a frame blanking period. Referring to FIGS.
9 and 10, memory 220 stores the LUTs of compensation data each at a
corresponding address. When an image is displayed in the [n]th
frame, the timing control part 210 receives a selection signal to
select an LUT of compensation data for overshooting in response to
change of environment (e.g., ambient temperature variation) from a
television receiver set through an I.sup.2C bus. The timing control
part 210 supplies an address of memory 220 to read the LUT
corresponding to the address from memory 220 through the I.sup.2C
bus. The LUT corresponding to the memory address is then stored in
the buffer 2260. Assuming that the number of the compensation data
of the selected LUT is `256`, a time period for transmitting the
compensation data is between about 10 ms and about 100 ms so that
the LUT may be changed without power-off of the LCD device.
[0095] The LUT stored in the buffer 2260 is written in memory 2280
during a blanking period, and then a data enable signal DE
corresponding to the [n+1]th frame is applied so that an image is
displayed using the LUT stored in memory 2280. The frame is changed
during the blanking period. The compensation data of the LUT stored
in the buffer corresponding to the ambient temperature is written
in memory 2280 during the vertical synchronizing signal is applied
to the timing control part. Thus, the compensation data for
improving the response speed of the liquid crystal is changed
without turning off the electric power of the LCD device.
[0096] When the primary gray-scale signal includes 16 gray-scale,
the primary gray-scale signal includes 256 gray-scale data so that
the size of an LUT for overshooting is minimized. That is, the time
period required for the 256 gray-scale data may be short so that
the compensation data stored in the buffer is stored in memory 2280
during the blanking period. In addition, a time period required for
selecting the LUT and applying the selected LUT is no more than
about 16.7 ms. Therefore, a user may not sense the variation of the
image in response to the variation of the LUT.
[0097] FIG. 11 is a schematic diagram illustrating the LUTs of
compensation data stored in memory 220 of the LCD device in FIGS. 5
and 7 and checksum data of the LUTs. Referring to FIG. 11, the LUTs
are stored in memory 220 (e.g., EEPROM) such that each LUT has its
own address to be stored therein. In other words, each LUT is
stored at a corresponding address in the memory. Thus, when the
timing control part reads a selected LUT from the memory in
response to variation in the ambient temperature and the vertical
synchronizing signal, the timing control part 210 only reads the
selected LUT by accessing the corresponding address instead of
reading the whole LUTs stored in the memory.
[0098] To prevent an error in reading a selected LUT from the
memory, the memory includes, for example, checksum data assigned
for the LUTs. The checksum data includes multiple sub-checksum data
each assigned to corresponding one of the LUTs. Thus, each LUT is
stored in the memory in association with corresponding sub-checksum
data.
[0099] For example, assuming that one LUT has the 256-bit size, if
LUT `A` is stored at address 301 to 556, sub-checksum data of the
LUT `A` is stored at address 556 to 557. In like manner, if LUT `B`
is stored at address 557 to 812, sub-checksum data of LUT `B` is
stored at addresses 812 to 813.
[0100] By using the checksum data, gray-scale data corresponding to
a selected LUT is stored in memory 2280 (referring to FIG. 9)
without an error on the gray-scale data. This is because the timing
control part repeatedly reads the selected LUT until no error is
detected from the gray-scale data corresponding to the selected
LUT.
[0101] The multiple sub-checksum data have values different from
each other. In other words, the sub-checksum data corresponding to
LUT `A` is different from the sub-checksum data corresponding to
LUT `B`. Also, total checksum data is stored at the last address of
the memory.
[0102] Having described the exemplary embodiments of the display
system according to the present invention, modifications and
variations can be readily made by those skilled in the art in light
of the above teachings. It is therefore to be understood that,
within the scope of the appended claims, the present invention can
be practiced in a manner other than as specifically described
herein.
* * * * *